Fixed #28585 -- Calculated admin's change form multipart context variable from forms and formsets

Thanks Tim Graham for the review.

django/contrib/admin/options.py

@@ -1061,7 +1061,10 @@ class ModelAdmin(BaseModelAdmin):
             'has_add_permission': self.has_add_permission(request),
             'has_change_permission': self.has_change_permission(request, obj),
             'has_delete_permission': self.has_delete_permission(request, obj),
-            'has_file_field': True,  # FIXME - this should check if form or formsets have a FileField,
+            'has_file_field': context['adminform'].form.is_multipart() or any(
+                admin_formset.formset.form().is_multipart()
+                for admin_formset in context['inline_admin_formsets']
+            ),
             'has_absolute_url': view_on_site_url is not None,
             'absolute_url': view_on_site_url,
             'form_url': form_url,

tests/admin_views/tests.py

@@ -56,10 +56,11 @@ from .models import (
     UnorderedObject, Villain, Vodcast, Whatsit, Widget, Worker, WorkHour,
 )
 
-
 ERROR_MESSAGE = "Please enter the correct username and password \
 for a staff account. Note that both fields may be case-sensitive."
 
+MULTIPART_ENCTYPE = 'enctype="multipart/form-data"'
+
 
 class AdminFieldExtractionMixin:
     """
@@ -3522,6 +3523,13 @@ class AdminInlineFileUploadTest(TestCase):
         self.picture = Picture(name="Test Picture", image=filename, gallery=self.gallery)
         self.picture.save()
 
+    def test_form_has_multipart_enctype(self):
+        response = self.client.get(
+            reverse('admin:admin_views_gallery_change', args=(self.gallery.id,))
+        )
+        self.assertIs(response.context['has_file_field'], True)
+        self.assertContains(response, MULTIPART_ENCTYPE)
+
     def test_inline_file_upload_edit_validation_error_post(self):
         """
         Inline file uploads correctly display prior data (#10002).
@@ -3658,6 +3666,10 @@ class AdminInlineTests(TestCase):
         response = self.client.get(collector_url)
         self.assertContains(response, 'name="widget_set-0-id"')
 
+        # No file or image fields, no enctype on the forms
+        self.assertIs(response.context['has_file_field'], False)
+        self.assertNotContains(response, MULTIPART_ENCTYPE)
+
         # Now resave that inline
         self.post_data['widget_set-INITIAL_FORMS'] = "1"
         self.post_data['widget_set-0-id'] = str(widget_id)
@@ -5451,7 +5463,7 @@ class AdminKeepChangeListFiltersTests(TestCase):
 
         # Check the form action.
         form_action = re.search(
-            '<form enctype="multipart/form-data" action="(.*?)" method="post" id="user_form".*?>',
+            '<form action="(.*?)" method="post" id="user_form".*?>',
             force_text(response.content)
         )
         self.assertURLEqual(form_action.group(1), '?%s' % self.get_preserved_filters_querystring())
@@ -5515,7 +5527,7 @@ class AdminKeepChangeListFiltersTests(TestCase):
 
         # Check the form action.
         form_action = re.search(
-            '<form enctype="multipart/form-data" action="(.*?)" method="post" id="user_form".*?>',
+            '<form action="(.*?)" method="post" id="user_form".*?>',
             force_text(response.content)
         )
         self.assertURLEqual(form_action.group(1), '?%s' % self.get_preserved_filters_querystring())